1. Field of the Invention
The present invention relates to a frame unit of a spread illuminating apparatus used as an illuminating means for a reflection-type display.
2. Description of the Related Art
A liquid crystal display featuring low profile, small occupied volume and light weight is used for many electrical products such as mobile phones and personal computers, and the demand thereof has been increased. Since a liquid crystal which is a component of the liquid crystal display does not emit light by itself, an illuminating means for a liquid crystal is separately required besides the liquid crystal display when used in dark places where solar or room light is not satisfactorily available. Thus, this illuminating means is desired to be compact in size and small in power consumption. In recent years, a thin plate-like spread illuminating apparatus of side light type (light conductive member type) is often applied in the liquid crystal display.
FIG. 9 shows an embodiment of a conventional spread illuminating apparatus of side light type.
As shown in the figure, a spread illuminating apparatus 1xe2x80x2 is generally composed of a transparent substrate 2 made of a light-transmissible material and a bar-like light source 5 disposed close to an end surface 8 of the transparent substrate 2. Light rays emitted from the light source 5 are introduced into the transparent substrate 2, and then reflected to illuminate a liquid crystal display (not shown) disposed under the transparent substrate 2.
The light source 5 is composed of a bar-like light conductive member 3 made of a transparent material and a spot-like light source (e.g. a light-emitting diode) 4 disposed facing one end of the light conductive member 3. The light conductive member 3 is provided with an optical path conversion means 12. The optical path conversion means 12, which makes light rays emitted from the spot-like light source 4 incident uniformly onto the end surface 8 of the transparent substrate 2, has grooves triangular in section on a surface opposite to a surface 9 facing the end surface 8 of the transparent substrate 2. The light conductive member 3 is disposed with the surface 9 running along the end surface 8 of the transparent substrate 2 at a predetermined distance therefrom.
The thickness of the transparent substrate 2 gradually decreases with the increase in distance from the end surface 8, forming the section of the transparent substrate 2 into a wedge-shape. A light reflection pattern 59 is formed on an upper surface 65 of the transparent substrate 2. The light reflection pattern 59 comprises grooves 57 triangular in section and flat portions 58 adjacent thereto, both formed parallel to the light conductive member 3 with predetermined intervals between each other. The grooves 57 are formed to vary in depth from each other so that light coming from the light conductive member 3 is reflected in a substantially uniform manner at a whole surface of the transparent substrate 2 irrespective of the distance from the light conductive member 3 (the light source 5) thereby uniformly illuminating the liquid crystal display (not shown) provided under the transparent substrate 2. Namely, the depth of the grooves 57 increases gradually in proportion to the increase in distance from the light conductive member 3.
A light reflection member (frame) 13 is provided so as to cover the light conductive member 3 for efficiently guiding light rays emitted from the spot-like light source 4 into the transparent substrate 2, protecting the light conductive member 3 against damages due to contact with other components, and preventing the light conductive member 3 from getting dust. The frame 13 is formed by bending in an approximately U-shape and is attached in such a manner as to cover longitudinal peripheral surfaces of the light conductive member 3 except the surface 9 facing the transparent substrate 2. Further, upper and lower opposing plates 13e, 13f of the frame 13 are inclined inwardly so as to have a predetermined angle from a direction perpendicular to a base plate 13g of the frame 13. When the frame 13 is set, the frame 13 is disposed in such a manner that distal ends of the upper and lower opposing plates 13e, 13f (ends opposite to ends continuous with the base plate 13g) cover the ends of the upper and lower surfaces 65, 66, respectively. Since the upper and lower opposing plates 13e, 13f are inclined inwardly giving an elastic force, the frame 13 is adapted to clamp the transparent substrate 2 and thereby fixed thereto. The frame 13 is structured such that a hard resin product has on the inner surface thereof a film on which a metal such as silver is evaporated or a white film or that a metal plate of aluminum or stainless is bent.
The frame 13 may be fixed to the transparent substrate 2 by placing a double-faced adhesive tape 54 on either of their overlapping portions, for instance, at the ends of the upper and lower surfaces 65, 66 of the transparent substrate 2.
However, the above conventional art has the following problems.
In the method of fixing the frame to the substrate by means of its elastic force, since fixing force between components (transparent substrate, light conductive member, and spot-like light source) is weak resulting in the components getting easily out of position, a stable illumination effect may not be achieved. Further, since the weak fixing force makes it difficult to connect or assemble the frame with other components (e.g. a liquid crystal display and so on), and since the assembly work must be carried out carefully so that the frame does not contact with the transparent substrate or the light conductive member, the working efficiency deteriorates.
In the method using an adhesive tape, the overall thickness of the apparatus increases for the thickness of the adhesive tape, and an irregularity in surface exists at the edges the adhesive tape.
Moreover, the frame covers only the light conductive member and does not protect the spread illuminating apparatus entirely.
The present invention has been made in light of the above problems and the object of the present invention is to provide a spread illuminating apparatus which includes a frame unit capable of securely fixing its components thereby achieving a stable illumination effect.
In order to solve the problems, according to a first aspect of the present invention, in a spread illuminating apparatus comprising: a spread illuminating section in which a bar-like light source composed of a light conductive member and a spot-like light source disposed at an end of the light conductive member is provided close to and along one end surface or each of two end surfaces of a transparent substrate made of a light-transmissible material; and a frame unit, the frame unit covers peripheral portions of upper and lower surfaces of the spread illuminating section and surfaces of both ends of the spread illuminating section, at least one of which the bar-like light source constitutes. Here, the spread illuminating section means a part of a spread illuminating apparatus and is composed of a transparent substrate and at least one light source disposed on an end surface thereof (and a light reflection member if provided).
According to a second aspect of the present invention, in the spread illuminating apparatus described in the first aspect, the frame unit is composed of two frame sub-assemblies, which are fitted onto the spread illuminating section from respective ends of the spread illuminating section, and are coupled to each other. With this construction, the entire periphery of the spread illuminating section can be covered with the frame unit and thus the components constituting the spread illuminating section can be fixed reliably.
According to a third aspect of the present invention, in the spread illuminating apparatus described in the first or second aspect, openings may be formed in one frame sub-assembly and projections are formed in the other frame sub-assembly at respective portions overlapping each other, and the openings and the projections may be engaged with each other to couple the two frame sub-assemblies. With this construction, the coupling process can be facilitated and the respective components can be fixed with precision.
According to a fourth aspect of the present invention, in the spread illuminating apparatus described in the third aspect, the two frame sub-assemblies may be fitted detachably. With this construction, the frame sub-assemblies can be fitted or detached easily and thus the efficiency in possible rework during the assembly can be improved.
According to a fifth aspect of the present invention, in the spread illuminating apparatus described in any one of the first to fourth aspects, an end of the light source may be fixed to a stopper extending from the frame sub-assembly. With this construction, since the stopper can fix the spot-like light source in a predetermined position with respect to the light conductive member, light emitted from the spot-like light source can be guided efficiently into the light conductive member.
According to a sixth aspect of the present invention, in the spread illuminating apparatus described in any one of the first to fifth aspects, side surfaces of the spread illuminating section, which are not covered with the frame sub-assemblies, may be fixed to stoppers extending from the respective frame sub-assemblies. With this construction, since the stoppers extending from the frame sub-assemblies can fix the transparent substrate constituting the spread illuminating section in a predetermined position with respect to the light conductive member, light emitted from the light source (the light conductive member) can be guided efficiently into the transparent substrate.
According to a seventh aspect of the present invention, in the spread illuminating apparatus described in any one of first to sixth aspects, an FPC, on which chip components including the spot-like light source are mounted, may be housed in the frame sub-assemblies.
According to an eighth aspect of the present invention, in the spread illuminating apparatus described in any one of first to seventh aspects, the side surfaces of the spread illuminating section, which are not covered with the frame sub-assemblies, may be covered with additional frame members.
According to a ninth aspect of the present invention, in the spread illuminating apparatus described in the eighth aspect, the additional frame members may be made of a non-conductive material.
According to a tenth aspect of the present invention, in the spread illuminating apparatus described in the eighth or ninth aspect, a dust-proof structure may be provided on the peripheral portion of the upper surface of the spread illuminating section.
According to an eleventh aspect of the present invention, in the spread illuminating apparatus described in any one of the eighth to tenth aspects, a sealing member may be stuck to the frame sub-assemblies covering the peripheral portion of the upper surface of the spread illuminating section and a transparent film for covering the entire upper surface of the transparent substrate is attached to the sealing member. With this construction, the film for covering the entire upper surface of the transparent substrate can be fitted easily and the spread illuminating apparatus can be provided with an airtight structure, thereby improving the dust-proof effect.